|Reuter, Ryan - TEXAS TECH UNIVERSITY|
|Galyean, Mike - TEXAS TECH UNIVERSITY|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 20, 2007
Publication Date: March 29, 2007
Citation: Reuter, R., Carroll, J.A., Galyean, M. 2007. Source and level of dietary energy influence responses to an endotoxin challenge in beef steers [abstract]. In: Proceedings, Plains Nutrition Council, Texas A&M University Publication No. AREC 07-20. p. 106. Technical Abstract: Twenty-four Angus x Hereford crossbred steers (250 ± 2.7 SE kg initial BW) were used in a completely random design with a 3 x 2 arrangement of treatments to determine the effects of level and source of dietary energy and antibiotic administration on performance and immune function. Steers were allotted to 1 of 2 antibiotic treatments (no treatment or tilmicosin phosphate s.c.) and 1 of 3 dietary treatments which were offered daily to individually penned steers. Dietary treatments (steam-flaked corn, alfalfa, and cottonseed hull base) were fed for the entire 49-d study period and consisted of a 30% concentrate diet fed ad libitum (30AL), a 70% concentrate diet fed ad libitum (70AL), and the 70% concentrate diet fed to provide equal calculated NEg intake to the 30AL treatment (70RES). Orts were weighed and quantity of feed to offer was calculated daily. Steers were housed individually in outdoor soil-surfaced pens for 21 d, housed indoors in stanchions for 10 d, and then returned to the outdoor pens for the final 19 d. On d 27, steers were catheterized in the jugular vein, and on d 28, an i.v. lipopolysaccharide challenge (LPS, 2 ug/kg BW) was given (0 h) to induce an acute-phase immune response. Blood samples were collected on 30-min intervals from -2 to 6 h, and again at 8 and 12 h after the challenge, and serum cortisol concentrations were determined. Rectal temperature was recorded at 1-min intervals during the challenge using an indwelling, automatic rectal temperature probe. A subjective morbidity score (0 = normal to 4 = moribund) was assigned to each animal on 1-h intervals from 1 to 6 h after the challenge. In response to the LPS challenge, steers on the 30% diet had greater cortisol (P = 0.03) concentrations than steers on the 70% diet treatments. The 30% diet also increased both cortisol production (amount and peak time) and subjective severity score compared with the 70% diet treatments. No effect of level of NEg intake was detected for these variables; however, increased NEg intake increased rectal temperature response (P = 0.04). No significant effects or interactions were detected for antibiotic treatment with respect to these variables.